I've imported some pictures to my "My Pictures" folder using Adobe Lightroom, but the Pictures app doesn't seem to notice the new files? Is there some way to force it to refresh its library?

To be clear,

Pictures are sorted under C:\Users\<username>\Pictures\ by year, then date; for example: C:\Users\<username>\Pictures\2012\2012-10-20, these show, however those in C:\Users\<username>\Pictures\2012\2012-10-29 do not, despite coming from the same camera, being in the same format, thumbnails working in Exporer, the pictures opening in the Pictures app via a double click in explorer, and Windows Media Centre having no problems.

I have tried excluding the Pictures library, and reincluding it, but that had no effect. It has taken three or four reboots for even the folders to show up in the app, but it reports them as empty

I have found that I can get the Photos app (and/or search indexer) to refresh the index to include photos that were newly added to a folder, by going to the folder in Windows Explorer, and explicitly opening one of the new photos from there with the Photos app.